Thermal Air Flow Sensor Ventilation Path Design
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Solution Overview
Problem
In physical quantity measurement devices, particularly thermal air flow rate sensors, there is a need to prevent the sealing of cavity portions on the back surface of the diaphragm while improving measurement accuracy.
Innovation Solution
A thermal air flow rate sensor with a ventilation flow path and a lead frame that includes a mounting surface and a flow passage forming member, where the ventilation flow path is formed by through holes on the lead frame and a connection flow path between the lead frame and the flow passage forming member, preventing the sealing of the cavity portion and enhancing measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a communication passage is formed by a groove provided in the support member and a lead frame to ventilate the cavity region, then the cavity portion on the back surface side of the diaphragm is prevented from being sealed, but the measurement accuracy of the thermal air flow rate sensor is insufficient
Solution Approach 1:
The ventilation flow path is divided into multiple segments: a first through hole communicating with the cavity portion, a second through hole opened on the mounting surface, and a connection flow path between them. This segmented approach allows precise control of airflow while maintaining cavity ventilation, thereby improving measurement accuracy without compromising reliability.
Solution Approach 2:
The ventilation flow path extends through multiple dimensions of the lead frame structure, utilizing vertical and horizontal pathways. The first through hole provides vertical communication with the cavity, while the connection flow path and second through hole provide additional dimensional routing. This multi-dimensional approach optimizes both ventilation effectiveness and measurement accuracy.
2Strength
If the cavity portion on the back surface side of the diaphragm is sealed, then the structural integrity is improved, but the thermal air flow rate sensor cannot function properly due to lack of ventilation
Solution Approach 1:
The lead frame structure implements local quality by providing ventilation only in specific regions where needed. The first through hole is positioned to communicate with the cavity portion requiring ventilation, while other regions maintain structural integrity. This localized approach allows the majority of the structure to remain sealed and strong, while specific areas provide necessary airflow for sensor functionality.
Solution Approach 2:
The connection flow path acts as an intermediary between the first through hole and the second through hole, mediating the airflow to the cavity portion. This intermediary structure allows controlled ventilation through the lead frame without compromising the overall structural integrity, as the flow path is designed to minimize structural weakness while maintaining airflow functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively prevents the sealing of the cavity portion on the back surface of the diaphragm, thereby improving the measurement accuracy of the thermal air flow rate sensor compared to existing technologies.
Implementation Method 1
The semiconductor element has a heating resistor formed in a diaphragm
Implementation Method 2
The semiconductor element has a heating resistor formed in a diaphragm
Implementation Method 3
thermal air flow rate sensor
Data Source
AI summary
A physical quantity measurement device is configured to seal a cavity portion on a back surface side of a diaphragm of a thermal air flow rate sensor while improving measurement accuracy. The device may include a lead frame having a mounting surface on which a flow rate sensor which is the thermal air flow rate sensor is mounted, and a flow passage forming member disposed on a back surface opposite to the mounting surface of the lead frame. A ventilation flow path is formed by a first through hole in communication with a cavity portion of the flow rate sensor, a second through hole provided in the lead frame and opened in the mounting surface, and a connection flow path that is defined between the lead frame and the flow passage forming member and connecting the first through hole and the second through hole.